Bellows or diaphragm pumps having a single pump section are well known in the art. In these devices the discharge and suction strokes are alternately produced by the reciprocating motion of the pump action element, i.e. the diaphragm or bellows. As a result, pulses of fluid are discharged from the pump and the pressure of the fluid being discharged from such pumps varies greatly. Such variations are undesirable in that they can cause pipe connections on the discharge side of the pump to be loosened, or cause "knocking" of the pipes thereby creating undesired noise In addition the variations in pressure can cause impurities which may accumulate on the interior wall of the discharge pipe to be peeled therefrom. Finally, if there is a filter in the discharge pipe, the pressure variations can cause enlargement of the filter openings thus lowering the capture rating of the filter.
Also known in the art are bellows or diaphragm pumps having a pair of pump sections with the pump action elements of the two sections being interlocked so that a discharge stroke of one pump section coincides with a suction stroke of the other pump section. Such pumps may have a common discharge passageway and a common suction passageway for the two pump sections. It would at first appear that since one pump section executes a discharge stroke while the other executes a suction stroke, or vice versa, there would be a continuous discharge hence fairly constant pressure should be present in the discharge passageway. However, this is not true in actual practice since it takes the action elements a finite time to stop and change direction. During this change-over interval, which occurs at the same time for both pump section, the pressure in the discharge passageway drops drastically. As a result, there are large pressure variations in the discharge passageway with the same undesirable consequences mentioned above.
To solve the problem of pressure pulsations in the discharge, it has been conventional to provide a pressure regulator or accumulator on the discharge side of the pump. While this reduces the pressure variations, it adds cost to the pumping equipment and complicates construction.